1. Field of the Invention
This invention relates to a time indicator and, in particular, to a time indicator which provides a clearer indication of expiration.
This invention also relates to patterned indicators, wherein latent information is contained within a pattern. The latent pattern is revealed upon the application of an activator or stimulus to the pattern.
In particular, this invention relates to an indicator wherein the relative amount of time that has elapsed from the initial activation of the indicator can be rapidly and easily determined by the progression of a visually perceptible change in color along different areas of the indicator.
This invention further relates to indicators wherein a latent pattern hidden in an array is brought forth upon application of activator or stimulus or after a period of time to reveal or conceal information. This invention also relates to a novel means for adjusting selected time periods for such indicators.
2. Prior Art
Numerous devices are known which provide a visual indication of the passage of a pre-arranged amount of time. Such time indicators are useful, for example, when attached to perishable items for indicating the length of time the items have been on the wholesaler's or retailer's shelf. Thus, foods, photographic materials and other perishable items can be provided with indicators which after being activated, evidence a visual change, after the passage of a predetermined period of time. Time-temperature indicators are also known which indicate a visual change as a function of both time and temperature. Virtually any time indicator however is also, at least to a minor extent, dependent upon temperature.
A preferred prior art time indicator is described in U.S. Pat. No. 4,903,254 to Haas and U.S. Pat. No. 4,212,153, of Kydonieus et al. This invention is an improvement on the invention described in these patents.
U.S. Pat. No. 4,212,153 to Kydonieus et al. describes a laminated time indicator including a two-layer front indicator part and a two-layer rear reservoir part. The front indicator part has an indicator layer with an outer display surface and an inner surface having an adhesive layer thereon. For example, a pressure-sensitive adhesive coated onto an opaque barrier layer such as vinyl. The rear reservoir part has a dye or ink film layer and a support card layer. When assembled, the front part is placed on the rear part with the ink film layer forming an assembly joint with the adhesive layer. The dye or ink dissolves in the adhesive. After a period of time, the ink migrates from the ink film layer through the adhesive layer and through the indicator layer to be displayed on the outer surface. In one day, for example, the dye or ink may only reach 20% to 30% of its potential color capacity due to the gradual migration (or adsorption) of the dye into the opaque indicator layer and due to the fact that as the concentration of dye increases at the surface, the process rate decreases. Thus, there is no clear indication of when the indicator expires. It is believed that the reason this prior art device has such deficiencies is due to the fact that the opaque indicator layer must be relatively thick to provide mechanical strength. Such thickness creates a long path through which the dye or ink must migrate, this causing a gradual darkening of the indicator. Further, the opaque indicator layer must have a relatively large quantity of filler, e.g. titanium dioxide, to make it opaque. This filler intermixes and/or adsorbs the dye as the dye migrates through the indicator layer and dilutes or decreases the intensity of the dye. Thus, a red dye or ink will mix and/or be adsorbed with the titanium dioxide and become pink. Kydonieus et al also further describes the use of a step-wedge test color panel placed next to the indicator which is used to compare the developed color or shade. The step-wedge can be provided with indicia corresponding to the time period required to develop the color at each step of the wedge.
U.S. Pat. No. 4,903,254 to Haas is an attempt to resolve some of the problems presented by the time indicators of Kydonieus et al. In particular, Haas '254 describes a badge which includes a four-layer front part and a two layer rear part. The front part has, overlaying each other, (1) a transparent front support layer with a front print display surface, (2) an ink display layer with a front ink display surface, (3) an optical barrier layer; and (4) an adhesive and ink dissolver layer. The rear part has (1) an ink film layer overlaying (2) a backup member layer.
Upon issuance of the badge, a release sheet is peeled off the front part and it is overlaid and pressed down upon the rear part, with the adhesive and ink dissolver layer and the ink film layer forming an assembly joint therebetween. This causes the ink dissolver and ink film to mix. The ink then migrates from the ink film layer, through the assembly joint, through the ink dissolver layer, through the optical barrier layer, through the adhesive and ink display layer to the front ink display surface, where it forms, for example, expiration notice words and diagonal voiding bars at the expiration of the time interval. A viewer can see the user's name and category on the front print display surface, as placed thereon when issued. Upon expiration, after a predetermined period of time, the viewer can see the expiration notice words and diagonal voiding bars on the front ink display surface behind the front print display surface. As can be readily seen from the foregoing, such a structure is complex and relatively difficult to manufacture.
Applicant is aware of the following additional prior art, none of which teach or suggest the invention claimed herein.
U.S. Pat. No. 2,337,534 to Barber, describes a magazine page exposure time indicator which includes a photosensitive paper sheet mounted on a magazine page, and a developed photographic film sheet having a series of adjacent portions of varying density mounted over the photosensitive paper sheet.
U.S. Pat. No. 3,018,611 to Biritz describes a time indicator device which may be used for frozen foods, parking, construction sites, etc. The device comprises a backing which is attachable to the outer surface of, for example, a package of frozen food. Superimposed on the backing is a strip of filter paper having a chemical reagent laminated thereto. The chemical reagent is an oxygen reactive material. The strip is hermetically sealed by a covering of transparent, impervious pressure sensitive cellophane which allows visual inspection of the oxygen reactive layer. A pin-hole size opening is provided in the covering to allow for ingress of air within the interior of the container. This opening is sealed by a removable tape. When the tape is removed the oxygen reactive material reacts to change color by permitting air to enter and diffuse into the container to make contact with the material. The pin-hole opening is provided at one end of the container and as time proceeds, the color proceeds toward the other unexposed end of the container.
U.S. Pat. No. 3,078,182 to Crone, Jr., describes a heat-sensing, color-changing, adhesive tape for a device to be sterilized in a hospital autoclave including an adhesive layer for attachment, a backing web over the adhesive layer and a visible colored layer over the backing web wherein the colored layer comprises a selective pigment dispersed in a resin binder.
U.S. Pat. No. 3,480,402 to Jackson, describes a time indicator formed of an absorbent carrier having absorbed thereon at least one chemical compound which changes color upon exposure to oxygen. The carrier and chemical compound absorbed thereon are protected from ambient oxygen by a non-perforated barrier layer which is transparent and through which atmospheric oxygen can controllably diffuse over a preselected period of time. Thus, when the chemical compound changes color, the preselected period of time is indicated. The graduated time indicator may be produced by utilizing more than one chemical or a layer covering the various pieces of absorbent material of different thickness. For each piece of absorbent material, the chemical absorbed on the piece of absorbent material would change color at different times, e.g., the chemical on one piece would change color after, say, one week, and the chemical absorbed on another piece would change color after ten days, and the chemical on a further piece of absorbent material would change color after fourteen days. Thus, a graduated time indicator is described.
U.S. Pat. No. 3,520,124 to Meyers, describes a parked car time indicator including a first sheet having a first reactant and a second sheet having a second reactant and a release sheet which is peeled away to permit contact of the first sheet with the second sheet to start a reaction over a selective time interval terminating with a color change of the reactants.
U.S. Pat. Nos. 3,954,011 and 3,962,920 to Manske, describes a time indicating device suitable for visibly measuring parameters such as time, temperature and time-temperature relationships. The device includes a porous fluid-carrying pad, a wick material for the fluid and an indicator means whereby the progress of fluid along the wick material can be visibly indicated and used to measure the passage of time, the exposure to a given minimum temperature or time-temperature relationship.
U.S. Pat. No. 3,999,946 to Patel, describes a perishable product time-temperature history indicator including a substrate for attachment to the product showing changes in temperatures along a y-coordinate over periods of time along an x-coordinate.
U.S. Pat. No. 4,028,876 to Delatorre describes an apparatus for visually indicating elapsed time by a color change which comprises a transparent container having a rupturable capsule therein and in which a first composition is contained. A transparent matrix surrounds the second composition which is also in the container. The device may be secured to a surface by means of a mechanical fastener or an adhesive layer.
U.S. Pat. No. 4,229,813 to Lilly. et al describes a time indicator which utilizes a silicon oil which is slowly absorbed onto and moves up a porous strip at a rate which is a function of time. One side of the strip is printed with an oil soluble ink, while the other side is unprinted. The printed side of the strip is laminated with polyethylene film to an unprinted strip. As the silicon oil moves up the strip, the oil contacts the ink causing a dye in the ink to migrate from the printed side to the unprinted side, thus providing a measurable color front moving up the strip.
U.S. Pat. No. 4,382,700 to Youngren describes an indicator which contains a mineral jelly which is in contact with a wick, such that the mineral jelly diffuses into the paper in accordance with the changes in ambient temperature over a period of time.
U.S. Pat. No. 4,408,557 to Bradley, et al describes a timer comprising an absorptive layer disposed on a base layer which accepts a carrier mixture at a predetermined rate. A barrier means is disposed between the carrier mixture and the absorptive layer, and the removal of the barrier activates the timer.
U.S. Pat. No. 4,629,330 to Nichols describes a color change indicator which includes a liquid which evaporates over a period of time and has a predetermined index of refraction, a reservoir for holding the liquid, and an opacifying layer of microporous material. The microporous layer has an index of refraction approximately the same as that of a liquid, overlies the reservoir and has an open cell network of pores for absorbing liquid from the reservoir. The layer is one color when the liquid occupies the layer, and a second color when the liquid is depleted from the layer.
U.S. Pat. No. 4,643,122 to Seybold, describes a tamper-indicating security tag including a carrier material impregnated with a solution of a selective compound with a solvent for use in a sealed enveloping container which controls the rate of diffusion of the solvent.
U.S. Pat. No. 4,646,066 to Baughman, describes an environmental exposure indicator device. The device includes a target made of a tuned circuit, a selective element which receives an interrogation signal in the radio or microwave frequency range and an antenna which receives and converts the signal to an electrical current. The selective element has an electrical property that changes in response to an environmental exposure, such as temperature, combined time-temperature, humidity, radiation, a particular fluid, or mechanical shock.
U.S. Pat. No. 4,737,463 to Bhattacharjee, describes a photoactivatable time-temperature indicator comprising a mixture of a thermally unreactive diacetylenic compound and a photosensitive compound that, on exposure to actinic radiation, forms an acid that converts the diacetylene to a thermally reactive product.
One of the problems associated with all of the foregoing devices, aside from the problems discussed relating to the Kydonieus et al and Haas patent, is that they are complicated to adjust for a selected period of time. Adjustment often involves experimentation with many types of chemicals, inks, solvents, wicks, etc. to prepare a device which can operate under the conditions expected. Additionally, very few of these devices can indicate the relative length of time that has elapsed since the device was activated, i.e., it is difficult to determine what fraction of the selected period of time has elapsed. Most of the prior art devices gradually change color over a period of time and involve, at best, a guess on how much time has elapsed. When this is combined with the possible variations in temperature, humidity, etc. that may exist in the environment of the time indicator, the viewer has very little confidence that he is close to the expiration time of the device.
A need thus exists for an indicator which is inexpensive, simple to construct and can clearly, relatively accurately and quickly indicate the lapse of progressive selected periods of time increments.
Also, there is a need for indicators which provide information upon the passage of discrete time intervals.
Further, there is a need for self-expiring or self-canceling tickets to prevent reuse and counterfeiting. Still further, there is a need for a means for easily adjusting the selected period of time without cumbersome trial and error methods.
In a related aspect of this inventions, there is also a need for maintaining the security of sealed packages. Enormous sums are lost each year by industry from theft occurring during transportation of goods in packages. Thieves simply open the packages in which goods are transported, remove goods, and reseal the packages. The unwary purchaser is thereby victimized. There is thus a need for tamper indicating security means which requires merely a brief visual inspection of the package in which the goods are transported to determine whether the package has been tampered with.